Evaluation of Bcr/cflA Targeted Efflux Inhibitory Potential of 2-Hydroxy-4-Methoxybenzaldehyde Against Proteus mirabilis

Amidst the challenge posed by multiple drug-resistant (MDR) bacteria, this study investigates the efficacy of 2-Hydroxy-4-methoxybenzaldehyde (HMB) as an efflux pump inhibitor (EPI) against Proteus mirabilis. Efflux pump-mediated drug resistance stands as a major obstacle in combating MDR strains, prompting the exploration of innovative strategies. P. mirabilis, a Gram-negative bacterium renowned for urease production, forms crystalline biofilms in catheterized urinary tracts, leading to encrustation and blockage. The Bcr/cflA efflux system, which promotes P. mirabilis biofilm development, is targeted for intrinsic antibiotic resistance inhibition. HMB's antibiofilm potential against P. mirabilis crystalline biofilm stems from its efflux inhibition on the Bcr/cflA efflux system. An antibiotic susceptibility assay unveiled HMB’s ability to enhance antibiotic sensitivity in P. mirabilis. HMB demonstrated putative efflux inhibition against P. mirabilis, with a maximum efflux inhibitory concentration (MEIC) of 50 μg/ml determined through EtBr accumulation assays. Molecular modeling indicated favorable interactions between HMB and the Bcr/ClfA efflux system, suggesting its potential as an EPI. HMB treatment down-regulated efflux genes expression and enhanced antibiotic susceptibility, particularly against amikacin, chloramphenicol, kanamycin, and polymyxin-B, highlighting its therapeutic role in combating antibiotic resistance in P. mirabilis.